Wave-focusing to subsurface targets using a switching time-reversal mirror

Abstract

The need for wave energy focusing to selected targets embedded within a host is commonly shared among various engineering fields, whether for stimulation and imaging in exploration geophysics, or for contaminant removal in geo-environmental engineering, or even for diagnostic/therapeutic purposes in medicine. In this paper, we are concerned with the feasibility of focusing wave energy to multiple subsurface targets embedded within a semi-infinite heterogeneous elastic host, by exploiting the time-reversibility of the lossless wave equation under adverse conditions for time reversal. Of particular interest for practical applications in geophysics is the need for a switching time-reversing mirror, where recorded Dirichlet data must be time-reversed as Neumann data due to equipment constraints. In the absence of theoretical guarantees, we turn to numerical experiments and report that wave-focusing can be indeed realized, despite various departures from the theoretically ideal time reversal case.